The gas that is a product of respiration is carbon dioxide (CO2). During cellular respiration, organisms, including animals and humans, convert glucose and oxygen into energy, releasing carbon dioxide and water as by-products. This process is vital for the production of ATP (adenosine triphosphate), which cells use for energy. In contrast, plants perform photosynthesis, absorbing carbon dioxide and releasing oxygen during the day, thus playing an essential role in maintaining the balance of these gases in the atmosphere. The interplay between respiration and photosynthesis is crucial for sustaining life on Earth.